either

[Andrei Alexandrescu]

On 1/9/11 3:13 PM, Tomek Sowiński wrote:
> Andrei Alexandrescu napisał:
>
>> Aha, so this encodes the predicate in the operation. With a general
>> predicate, that would be:
>>
>> if (any!"a != b"(expr, 1, 2, 5)) { ... }
>>
>> The advantage over
>>
>> if (expr != 1 || expr != 2 || expr != 5)) { ... }
>>
>> is terseness and the guarantee that expr is evaluated once (which is
>> nice at least for my code).
>
> Yes.
>
>> This looks promising and well integrated with the rest of Phobos. Should
>> I add it?
>
> Please do. Oh, thinking about it 10 more minutes, an improvement struck me:
>
> bool any(alias pred = "a==b", E, Ts...)(E e, Ts args) if(Ts.length>  1 || !isTuple!Ts) {
>       foreach (a; args)
>           if (binaryFun!pred(a, e))
>              return true;
>       return false;
> }
>
> unittest
> {
>       assert(!"abac".any("s"));
>       assert(!"abac".any("aasd", "s"));
>       assert("abac".any("aasd", "abac", "s"));
> }
>
> /// Unpacks a single tuple.
> bool any(alias pred = "a==b", E, T)(E e, T t) if(isTuple!T) {
>      return any!(pred, E, T.Types)(e, t.field);
> }
>
> unittest
> {
>       assert(any("abac", tuple("aasd", "abac", "s")));
>       assert(find!any([5,3,7,9,4,5,7], tuple(2,4,6)) == [4,5,7]);    // cool!
> }

Hm, I don't see why not asking the owner of the tuple to type .expand.

>> And if I do, is "any" the name?
>
> For a start. We can always vote it to sth more descriptive e.g. 'isAny' in case 'any' turns out misleading.

At best we'd minimize such jitter.


Andrei